1. Field of the Invention
The present invention relates to tape drives of the type having a unit that enables or disenables a function associated with data transfer or storage with respect to a magnetic tape in a cartridge inserted in the drive, wherein a microswitch is used to detect whether a sliding element on the tape cartridge has been manually actuated to close or block a recess in the tape cartridge.
2. Description of the Prior Art
Most cassettes or cartridges in which magnetic recording tape is spooled have an element that is accessible at the exterior of the cassette or cartridge housing that allows a user to prevent erasure of information already stored on the tape, or to prevent overwriting of existing information with new information. A common example of such an actuator is the breakaway tab on music recording cassettes and VHS cassettes. When such a cassette is inserted in a playback unit, the tab comes to be located adjacent a lever or a plunger of a small switch. As long as the tab is in place, movement of the plunger or the lever is prevented. When the tab is broken away by a user, the plunger or lever is then permitted to move into the recess that was previously blocked by the tab, thereby actuating the switch and disenabling the playback unit from operating in a particular manner, such as to erase data stored on the tape or to overwrite data stored on the tape.
In the case of tape cartridges for use in high-speed back-up tape drives, the cartridge housing typically is of a more rugged construction than a conventional plastic cassette housing. Such tape cartridges, instead of a breakable tab, typically have a recess at one surface of the cartridge, such as the bottom surface, that is opened or closed by a sliding element that is disposed in an adjacent wall of the cartridge housing, such as a lateral wall. Such a conventional tape cartridge 1 is shown in FIG. 1, having a recess 2 in the bottom thereof that is opened or closed by sliding a tab 5 back and forth. When the tab 5 is manually moved to open the recess 2, this permits the plunger 3 of a microswitch connected to a read/write control 4 to enter into the recess. The plunger 3 typically is spring-biased to move in a direction indicated by the double arrow that is substantially perpendicular to the sliding direction of the tab 5. When the tab 5 is moved to a position that closes or blocks the recess 2, the plunger 3 is not able to move into the recess.
The state of the microswitch (i.e. whether the plunger 3 has moved into the recess 2, or been prevented from moving into the recess 2) is detected by the read/write control 4, which then appropriately enables or disenables certain functions of the tape drive dependent thereon.
A problem with such conventional arrangements that make use of a sliding tab 5 is that the microswitch plunger 3 is small and relatively fragile, and can easily be bent or broken if it is located in the recess 2, and an attempt is then made to slide the tab 5 to the closed position. Not only does this situation present a risk of breakage of the plunger 3, but also it precludes changing the status of the functions that have been enabled or disenabled while the tape cartridge 1 is disposed in the tape drive. Many users would like to have the capability of actuating the tab 5 from an opened position to a closed position while the tape cartridge 1 remains in the tape drive.